The present invention relates to a disk device capable of writing servo data by itself (referred to as “self servo track write”) and a manufacturing method therefor, and more particularly to a disk device having increased head positioning accuracy and a manufacturing method therefor.
Known data storage devices use various types of media such as optical disks and magnetic tape. Among these data storage devices are hard disk drives (HDDs), which have been widely used as storage for computers and are now essential storage devices in computer systems. Their applications, however, are not limited to computers. Due to their superior characteristics, HDDs have found application in an increasing number of fields. For example, they have been used in video recording/reproducing apparatuses and car navigation systems and also used as removable storage (memory) for digital cameras.
Magnetic disks used in a HDD have a plurality of concentric tracks formed thereon, each track including data areas for storing data and servo areas for storing servo data. Specifically, the data areas store user data while the servo areas store address information (servo data). Data write or data read can be performed by causing a magnetic head formed of a thin-film element to access a desired area (address) according to address information.
The servo data stored in each servo area includes a cylinder ID, a servo sector number, and a burst pattern. A track ID indicates the address of a track, and a servo sector ID indicates the address of a servo sector. The burst pattern holds relative positional information on the magnetic head with respect to the track. A burst pattern is made up of a plurality of bursts (signals), each stored in a plurality of regions. These regions are arranged at regular intervals in a disk radial direction such that the bursts have different phases.
Data is written to or read from a magnetic disk while checking the position of the magnetic head over the rotating magnetic disk based on servo data. The servo data read by the magnetic head is processed by the controller. The controller determines the value of the current to be supplied to the voice coil motor (VCM) based on the relationship between the current magnetic head position and the target magnetic head position. The controller then generates control data (DACOUT) indicating the calculated current value, and inputs it to the VCM driver. In the positional control of the magnetic head, the carriage is driven so as to eliminate the difference between the current and the target magnetic head positions.
Recently, in order to develop a higher capacity HDD, there has been a tendency to reduce the track pitch and thereby increase the track density. Producing a narrow track requires writing the above servo data with high precision to accurately control the position of the head. Therefore, the servo track write (STW) process for writing servo data has become an extremely important production process. To enhance the positioning accuracy, higher-precision optical encoders have been used, or external STW devices have been used to write servo data to a separate disk to reduce mechanical vibrations. However, wind disturbance due to the rotation of the disk and disk flutter have now become two major factors in determining the accuracy of the servo track write operation; they are very difficult to reduce.
To solve the above problem, the specification of U.S. Pat. Application (laid-open) No. 2003/0081344 discloses a servo track writer which performs servo track write operation in a low density gas atmosphere. Specifically, the technique disclosed in the above patent document inserts a disk to which servo data is to be written into the servo track writer, replaces the air within the servo track writer with a low density gas such as He, and then performs an STW operation. Performing STW operation in a low density gas atmosphere reduces the disk vibration in the STW process.
Further, a proposed conventional method for reducing disk flutter is to produce and ship a HDD product filled with a gas lighter than air. See, for example, Japanese Patent Publication No. 60-59660. The technique disclosed in that patent publication removes air from within a hermetically sealed magnetic disk storage device and fills it with helium or hydrogen instead, which makes it possible to reduce windage loss and thereby prevent an increase in the internal temperature of the device due to use of a high density magnetic disk.